Raid 5 vs. Raid Z + HW vs. SW

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iknowsomestuff

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Sep 28, 2013
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Hello :),
I would like to build a small home server. Unfortunately I was not able to resolve my final questions, because I either find people aiming for HW or for SW RAID. So I am not able to make a good comparison. I hope you can help me.


There are 3 issues I am not sure about:
- Hardware or Software Raid
- Raid 5 or RAID Z
- Which CPU

My aims:
- have a decent home server that has much read/write speed
- I can use Truecrypt
- There's enough power to run SMB/FTP, OpenVPN, DLNA + audio streaming with encoding


1st Issue:
Is there any speed difference between HW and SW Raid?
Which one is more power consuming?
How easy can I extent the raid or rebuild it?
SW RAID: What happens when the OS crashes?

2nd Issue:
Which of both got the better performance?
For which reasons would you prefer RAID Z over RAID 5 and vice versa?
Can I use cache devices for both? (I only read that it's possible with RAID-Z, how about RAID5)

3rd Issue:
Which CPU has enough Power for Truecrypt and the other services?
Which one would you chose if one uses HW RAID, which one in case of SW RAID?

4th Issue:
Which OS?

Thank you very much for your help!

 
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drtweak

drtweak

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Sep 17, 2012
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1) Hardware Raid is WAAAY more superior. Go with that. Its automatic and just better to deal with than Software Raid. If you look up Raid online you'll see why. Too much detail to go into. Not that there isn't anything wrong with software raid just hardware is better. Its less CPU intensive if you have to rebuild.

2) haven't played with Raid Z before. I have plenty experience with Raid 0 1 5 and 6 and if you do choose raid 5 I would say take it an extra step futher if your raid card supports it and go Raid 6. Will tolerate a 2 drive failure. Me i'm more of a Raid 10 person but its more expensive.

3) haven't messed with Truecrypt either. But again if you choose hardware raid its less CPU intensive over software raid so you will get some better CPU performance on a hardware raid.

4) Well if you do software i think you have to at least have the Pro version of what ever windows (Unless its server). If you have a hardware raid it don't matter what you have on the hard drives. how its partitioned, file system, OS ect.
 
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F

FireWire2

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Oct 30, 2006
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With HW RAID you can scale back the CPU host , that in turn scale-back power consumption.
Like my 40TB media server only consumes 180W of power, and it can go to sleep to save even more energy

Due to data transfers via network, a decent NIC/Wifi Router are essential
with a SPM394 - 5 drives HW raid5 you can have a 16TB volume RAID5 (5x 4TBTB)
All of my clients NAS are using Intel NIC - Realtek can not beat that.

I was able to transfer 200MB/s with bonding NIC.
Here is my 180W NAS still in service
http://www.mpcclub.com/forum/showthread.php?t=22898&page=4
 
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A

axel_roland

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Jan 10, 2014
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That was true 10 years ago but things changed a bit when you look at the factor how fast processors are today on one side and what SOHO demands are on the other. On a "normal" small business office or at home you'll have a gigabit network capable of transferring round about 100mb/sec or say 200mb/sec with port trunking (which 90% of all users won't use anyway). You can max out those 100mb/sec with a software raid and a few-cents-atom processor.

Don't underestimate the chances a software RAID offers you. data handling routines implemented in Software can be far more complex than you would implement them in Hardware. Maybe I'm wrong but AFAIK there is no Hardware Implementation of RAID-Z on the market and probably there won't be - at least not in terms of the classic ultra high speed static hardware implementation. And RAID-Z is alien technology compared with your grand fathers RAID-5.

Don't get me wrong: Looking at the pure basics of say a RAID-5, sofware never beats hardware in terms of speed and cpu usage - that's a fact and I know that. But given the flexibility, compatibility and the real world demands today: hardware raid is so dead in my eyes in end user and small business environments.
 
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FireWire2

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That is not quite right!
Agree CPU power is increase with exponent scale, but time remain the same....

Each of HDD send 1000's IRQ per second to CPU when it runs... This in time will slow down the process.
Raid5 engine loaded has very little power draw from nowadays CPU to calculated the parity but it takes time from CPU

Put in a simple term.
A very efficient, powerful leader leads a bunch of workers, the worker's VERY MOVEMENT they have to get a confirmation from that leader. Now if you have 5x guys doing that all day to that leader.

Do you think that group is a good, high output group?

This is the same reason why the rebuild process software RAID5 takes days....particular with more the 4x HDD RAID's members

As far as "dirty. rotten bit" that is all in theory that scares all of us.

In actual work, if it happens, RAID engine will mark it as a BAD drive. which i think is better that way...
Because the built-in ERC (error correction code) can not fixed it, that HDD should not be in the RAID from the 1st place.
 
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